This research will examine the effect of anti-viral immunity against an oncogenic lymphotropic virus, Herpesvirus sylvilagus, on (1) the resistance to challenge with virulent virus, (2) alteration of the clinical disease, and (3) elimination of the chronic carrier state established by this agent in its natural host. This will include: 1. Use of attenuated live vaccine given by the oral route. 2. Use of inactive vaccine in peanut oil adjuvant given by the intramuscular route. 3. Combined use of the live and inactive virus vaccine.